1. Field of the Invention
The present invention relates to preparations of bird seed treated with a material containing capsaicin or capsaicin derivatives or analogues thereof (including resiniferatoxin (RTX) or RTX analogues) in an amount sufficient to be unpalatable to mammals (e.g., rodents), which have capsaicin receptors.
2. Description of Related Art
U.S. Pat. No. 779,634 by Allen discloses a poison composition for the extermination of rodents which are destructive to crops. The poison comprises one pound of cayenne pepper, three (3) gallons of bisulfid of carbon, and one gallon of carbolic acid. A piece of absorbent material is saturated with the preparation and placed in locations frequented by unwanted rodents.
U.S. Pat. No. 631,738 by Dowie discloses a powdered composition for expelling rats consisting of twenty percent chili pepper, five percent hellebore, eight percent sulphate of lime, eight percent phosphate of lime, fifty four percent carbonate of lime and five percent oxide of iron. The powdered composition is intended to be sprinkled on the premises where rats are troublesome, and as a result of its intense irritating and burning qualities effectually prevents the rats from again invading places where the composition has been used. The hellebore and pepper are mixed with a medium to form a very light powder so as to float on the air and permeate the areas where the rats may be. It is said to be impossible to use hellebore without the pepper as it would be unbearable to human beings distributing it.
U.S. Pat. No. 4,455,304 by Yaralian discloses a method and composition for repelling birds from crops by applying the composition in the vicinity of the crop to be treated. The composition comprises finely divided garlic and finely divided dried cayenne pepper, the garlic being present in at least about one-fifth to at least five times the weight of the pepper, dry weight, and the total amount of garlic and pepper applied being from at least about 0.37 to 3.7 kilograms per hectare.
Szolcsanyi et al, Pain, 27 (1986) 247-260, discloses the sensitivity of birds to the nociceptive action of capsaicin differs from that of mammals. This was investigated by local instillation of capsaicin into the eye and by close arterial injection in pigeons and guinea-pigs. More specifically, instillation of capsaicin into the eyes of the pigeons did not evoke more reactions than the solvent alone. Thus, pigeons were found to reveal selective insensitivity to capsaicin and the peripheral chemoreceptive nerve endings in pigeons are almost totally insensitive to capsaicin.
Capsaicin and its analogues have been commercially used as repellents, such as in HALT, an aerosol preparation sold to repel attacking dogs.
Monsereenvsorn et al (1982) CRC Crit. Rev. Toxicol. 10, 321-339, discloses the physical and chemical properties of capsaicin.
Rozin, P. and Schiller, D., "The nature and acquisition of a preference for chili pepper by humans", Motiv. Emot. 4, 77-101, 1980, teaches that the maximum tolerated dose of chili pepper for humans is between 1,300 Scoville units (1 part in 1.25.times.10.sup.4 of capsaicin) and 10,400 Scoville units (1 part in 1.5.times.10.sup.3 of capsaicin).
Rozin, P. and Gruss, L., and Berk, G., "Reversal of innate aversions: attempts to induce a preference for chili peppers in rats", J. Comp. Physio. Psychol. 93, 1001-1014, 1979, teaches that incorporation of chili pepper in the feed of rats at a level of 400 Scoville units (corresponding to 1 part capsaicin in 40,000) causes 95% rejection of the treated food relative to untreated food. The report further teaches that the geometric mean for the avoidance threshold is 1 part capsaicin in 1.5.times.10.sup.6 and that all animals (out of 12 tested) avoided the treated feed at an avoidance threshold of 1 part capsaicin in 25,000 in the feed.
Sann, H., Harti, G., Pierau, F. K., and Simon, E., "Effect of capsaicin upon afferent and efferent mechanism of nociception and temperature regulation in birds", Can. J. Physiol. Pharmacol. 65: 1347-1354, 1987, teaches that the acute capsaicin effects on nociception in chickens upon close arterial injection were only observed at a dose two to three orders of magnitude higher than that in mammals.
Kare, M. R., "The special senses" in Avian Physiology, P. D. Sturkie, Ed., Cornell University Press, Ithaca, N.Y., 1965, pp. 406-446, teaches that parrots willingly eat hot peppers.